Changes

==Diatoms==

==Diatoms==

[[file:applied-paleontology_fig17-6.png|300px|thumb|{{figure number|2}}See text for explanation.]]

[[file:applied-paleontology_fig17-6.png|300px|thumb|{{figure number|2}}Typical diatoms.]]

Diatoms are photosynthesizing protists that occur in both marine and nonmarine environments. Marine diatoms range from Late Jurassic or Early Cretaceous to Holocene and are particularly useful for age and environmental determinations in the late Cenozoic. Nonmarine diatoms range from Eocene to Holocene and also are useful in the late Cenozoic. These microfossils can be a major rock-forming group, forming sedimentary rock (diatomites) consisting primarily of diatoms. Diatomaceous sediments, when altered by burial diagenesis, are converted to siliceous shale, porcelanite, and chert. Such rocks can serve as sources and fractured reservoirs for hydrocarbons (e.g., Monterey Formation of California). The changes in rock properties associated with silica diagenesis permit seismic definition of silica-phase transformation zones in the subsurface (e.g., bottom-simulating reflector).

Diatoms are photosynthesizing protists that occur in both marine and nonmarine environments. Marine diatoms range from Late Jurassic or Early Cretaceous to Holocene and are particularly useful for age and environmental determinations in the late Cenozoic. Nonmarine diatoms range from Eocene to Holocene and also are useful in the late Cenozoic. These microfossils can be a major rock-forming group, forming sedimentary rock (diatomites) consisting primarily of diatoms. Diatomaceous sediments, when altered by burial diagenesis, are converted to siliceous shale, porcelanite, and chert. Such rocks can serve as sources and fractured reservoirs for hydrocarbons (e.g., Monterey Formation of California). The changes in rock properties associated with silica diagenesis permit seismic definition of silica-phase transformation zones in the subsurface (e.g., bottom-simulating reflector).